1. Field of the Invention
The present invention relates generally to the field of satellite antennas. More specifically, the present invention discloses a deployable satellite antenna intended especially for use on a vehicle, such as a recreational vehicle.
2. Statement of the Problem
Antennas have enjoyed increasing popularity in recent years for the purpose of receiving television signals from orbiting satellites. Satellite antennas are perhaps most widely used in small towns and rural areas that are not served by cable television systems. However, a market for satellite antennas also exists for recreational vehicles, such as motor homes, campers, trailers, mobile homes, and the like, that can be moved to remote locations not serviced by conventional cable television systems. A number of special considerations come into play when adapting an antenna for use on such a vehicle. First, it should be possible to readily stow the antenna while the vehicle is traveling to minimize aerodynamic resistance and to reduce the risk of damage to the antenna, its ancillary equipment, and the vehicle resulting from aerodynamic loads and other road hazards. Second, the antenna should be able to be positioned to virtually any azimuth and elevation. With a conventional ground-based antenna, it is sometimes possible to accept a limited range of azimuths or elevations for an antenna given the known relative locations of the satellites and the antenna. In the case of an antenna mounted on a vehicle that can be moved over a wide geographic area and parked in any azimuth orientation, such restrictions are not acceptable and a full range of possible azimuth and elevation positions are necessary for the antenna. Third, the antenna system should be relatively compact while stowed and while deployed, so as not to interfere with any other objects (e.g., the air conditioning unit, vents, or luggage rack) located on the roof of a typical recreational vehicle. Finally, the system should be designed to use conventional electric motors to accurately control the motion of the mechanical linkages to position the antenna without discontinuities or singularities.
A number of deployable antennas have been invented in the past, including the following:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Sherwood et al. 5,337,062 Aug. 9, 1994 Tsuda 4,937,587 June 26, 1990 Yamada 4,887,091 Dec. 12, 1989 Bruinsma et al. 4,868,578 Sep. 19, 1989 Bisseff 4,811,026 Mar. 7, 1989 Radov 4,710,778 Dec. 1, 1987 Wilson 4,663,633 May 5, 1987 Shepard 4,602,259 July 22, 1986 Japan 60-260207 Dec. 23, 1985 Japan 60-260205 Dec. 23, 1985 Japan 60-233905 Nov. 20, 1985 Weir 4,490,726 Dec. 25, 1984 Sayovitz 4,309,708 Jan. 5, 1982 Japan 55-53903 Apr. 19, 1980 Budrow, et al. 3,739,387 June 12, 1973 Budrow, et al. 3,665,477 May 23, 1972 Budrow, et al. 3,587,104 June 22, 1971 Bergling 3,412,404 Nov. 19, 1968 "The Original Best Made Super-Sat RV Satellite Systems" advertisement, W. C. Laikam Co. Inc., Fresno, CA (circa ______________________________________ 1990).
The advertisement by W. C. Laikam Co. Inc. shows a satellite antenna system that can be mounted to the roof of a recreational vehicle. The elevation control mechanism includes a gear and linkage assembly driven by the elevation motor that automatically moves the feed arm to a stowed position when the dish is lowered and moves the feed arm to an extended position when the dish is deployed. This arrangement requires an elongated opening through the dish to accommodate the feed arm and one of the linkages. In addition, a coil spring extends from the feed arm and attaches to the face of the dish. Openings and attachments to the dish may be acceptable in older satellite antenna systems having a large dish (e.g., three to five feet in diameter). However, such irregularities in the reflective surface of the dish would significantly degrade performance in newer, smaller satellite antennas.
Sherwood et al. disclose a deployable satellite antenna for use on vehicles. The reflector is stowed in a face-down position with the feed horn protected beneath the reflector.
Tsuda discloses a low profile scanning antenna having an arcuately shaped track. A carriage supporting the antenna dish moves along the inside of the arcuate track.
Yamada discloses a receiving antenna for vehicles having a horizontally rotatable base plate with a main reflector tiltably attached to the edge of the base plate. A sub-reflector is mounted at the end of an arm extending from the base plate.
Bruinsma et al. disclose a portable reflector antenna assembly having a triangular base frame employing three beam members that are joined together at their ends with hinge-type knuckles that are slidably positioned on three legs. The frame can be adjusted on the legs for both height and leveling by virtue of the slidable movement of each of the knuckles along the legs. When the desired position is reached, the knuckles are clamped to the legs by means of lever-cam actuated draw bolts. The reflector is supported along its rim by pivotal supports and clamps. The bottom edge of the reflector is slidably adjustable in azimuth along the front beam member of the frame. The top edge of the reflector is supported for slidable elevation adjustment along a shaft 42 that extends upward from the rear leg 18.
Bissett discloses a mobile satellite receiving antenna especially for use on recreational vehicles. A generally cylindrical collar extends upward from the vehicle roof. A parabolic reflector is hinged along an edge to a horizontal turntable within the collar so that the reflector may be rotated to a concave downward position to serve as a weather cover over the collar and also to provide smooth aerodynamic conditions during transport.
Radov discloses a modular earth station for satellite communications having a frame adapted to be installed in an inclined roof. A concave antenna is adjustably mounted to the frame and covered by a rigid canopy.
Wilson discloses a vehicle-mounted satellite antenna system having a base plate mounted on the vehicle roof, a support member rotatably secured to the base plate to permit rotation about a vertical axis, and a parabolic reflector pivotably secured to the support member. A one-piece feed arm 56 is pivotally secured to one end of the parabolic reflector. When the antenna is deployed, the feed arm is automatically pivoted to a position in which the feed horn is coincident with the focus of the reflector. When the antenna is returned to its rest position, the feed arm is automatically pivoted so that the feed horn is retained within the confines of the interior surface of the reflector. Here again, the linkage 68 used to raise the feed arm 56 requires an opening 66 through the face of the dish.
Shepard discloses a polar mount for a parabolic satellite-tracking antenna.
Japanese Patent Nos. 60-260207 and 60-260205 disclose a vehicle-mounted antenna that can be stowed with the dish in a face-down position against the roof of the vehicle.
Japanese Patent No. 60-233905 discloses an antenna having a feed arm that permits the feed horn to be stowed in a position adjacent to the surface of the dish.
Weir discloses a collapsible rooftop parabolic antenna. The antenna has a horizontal pivot that provides axial displacement if axial wind forces on the antenna exceed a predetermined limit. This limits the torque transmitted to the roof on which the antenna is mounted to a reasonably low level.
Sayovitz discloses a foldable disk antenna supported on a framework resting on the bed of a truck or trailer. Folding legs on the framework can be extended to contact the ground to support the antenna.
Japanese Patent No. 55-53903 discloses a satellite antenna with a tracking system that allows the antenna to be stowed.
The patents to Budrow et al. disclose several embodiments of a TV antenna suitable for mounting on the roof of a recreational vehicle. The direction of the antenna can be controlled from the vehicle interior. In addition, the antenna dipoles can be folded to a closed position when the vehicle is transported.
Bergling discloses a dish reflector having a stowed position.
3. Solution to the Problem
None of the prior art references uncovered in the search show a deployable antenna system having the structure of the present invention. In particular, the linkage mechanism used in the present invention to automatically fold the feed arm assembly as the antenna is stowed is neither taught nor suggested by the prior art. The present system is especially suited for use with smaller reflectors due to the fact that the face of the reflector is left intact, without requiring openings or attachments. The present system is also simple and reliable, and has fewer exposed components.